Conventionally, in a known vehicle seat, a seat back is connected to a seat cushion via a reclining device (a locking device), so as to perform an adjusting operation of a backrest angle thereof Japanese Patent No. 3596010 described below discloses an example of a specific construction of the reclining device described above. In the description, the reclining device has a gear that is integrally formed in a frame of the seat back, and a pawl that is capable of linearly advancing and retreating with respect to a frame of the seat cushion. Upon meshing engagement of a toothed surface of the pawl with a toothed surface of the gear, the backrest angle of the seat back can be secured.
More particularly, both side portions of the above-described pawl are guided by raised wall-shaped guide walls formed in the frame of the seat cushion, so that the pawl can be supported to be slidable in the advancing/retreating direction described above. Formed between the pawl and both of the guide walls is small clearances for securing slidability of the pawl. The clearances may cause backlash in the pawl and both of the guide walls. The backlash may cause looseness in a locked condition between the pawl and the gear.
In view of this, in the reclining device described above, the pawl is obliquely divided into two pawl portions along the advancing/retreating direction. When the inner pawl portion positioned inside is pushed outwardly, the inner pawl portion and the outer pawl portion can be slid obliquely along inclined contact surfaces thereof in a direction in which they are spaced from each other, so that the clearances between the pawl and both of the guide walls can be cleared. Thus, the pawl and the gear can be in meshing engagement with each other, so as to be locked.
However, in the conventional technique described above, because the pawl is divided obliquely, in a condition in which the pawl and the gear are locked by meshing engagement, a load in a rotating direction applied to the outer pawl portion from the gear cannot be properly applied to the guide walls. In particular, when the load in the rotating direction is applied to the outer pawl from the gear, the load can be applied to the inner pawl portion after it is resolved into an inwardly-directed component via the inclined contact surfaces of the inner and outer pawl portions. As a result, an excessive load can be applied to an operational component such as a cam pressing the inner pawl from an inner side.
Thus, there is a need in the art to provide an improved locking device.